1. Field of the Invention
The invention relates to a heating device as described in the preamble to claim 1.
2. The Prior Art
A heating device is already known According to U.S. Pat. No. 4,279,255 A, which comprises a heating device by means of which heat is applied to a localised area of a body. In this case the heating device consists of a flexible heating unit, containing a plurality of electrical resistive heating elements which are supplied with electrical power by means of a battery inserted in a battery pack. For this purpose the battery is connected to the resistive heating element via an energy transfer device, particularly electrically conductive wires, the length of which is of such dimensions that the heating device can be located on body parts which are remote from the centre of gravity of the body. The battery pack with the inserted battery lies roughly at the centre of gravity of the body. Moreover, a switch member in the form of a selector switch is secured with the power supply device at the battery pack, and by means of which each resistive heating element can be switched on and off, so that the quantity of heat energy can be adapted to varying requirements. Furthermore the heating device has attachment means in order to locate the battery pack roughly at the centre of gravity of the body, and further attachment means by means of which the heating device can be located on a body part.
A disadvantage in this construction is that for long-term operation correspondingly large batteries are necessary due to a high energy requirement, and maintenance of a predetermined temperature is only possible within relatively large boundaries, so that the comfort of wearing the heating device is considerably reduced and in particular mobile use is rendered difficult.